Crypto trading bot: engine, brokers, backtester, dashboard, deploy

FastAPI backend with a single-strategy async engine, paper and Binance
brokers, pure-python indicators, a backtester that shares the engine's
portfolio math, and a Vue dashboard with a live WebSocket feed. Adds the
Gitea Actions CI/CD workflow that deploys to Traefik via docker_default.

backend/app/market/base.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+
+from app.schemas import Candle
+
+
+class MarketData(ABC):
+    """Read-only market data source (candles + last price)."""
+
+    @abstractmethod
+    async def fetch_candles(self, symbol: str, timeframe: str, limit: int) -> list[Candle]:
+        raise NotImplementedError
+
+    @abstractmethod
+    async def fetch_price(self, symbol: str) -> float:
+        raise NotImplementedError
+
+    async def close(self) -> None:
+        return None